Carbonaceous bonding system for regractories

ABSTRACT

CARBONACEOUS BONDING SYSTEM FOR REFRACTORIES, ESPECIALLY BASIC REFRACTORIES, OF INCREASED STORAGE LIFE, WHICH SYSTEM DOES NOT NORMALLY REQUIRE HEATING FOR USE. SAID SYSTEM BEING MAINLY COMPRISED OF UNSATURATED FATTY ACID PITCH PLUS AN EFFECTIVE AMOUNT OF THAT PORTION OF PITCHES GENERALLY REFERRED TO AS ASPHALTENES.

United States Patent C) 3,578,472 CARBONA'CEOUS BQNDIN G SYSTEM FOR REFRACTORIES George R. Henry, Bethel Park, and Ernest P. Weaver, Pittsburgh, Pa., assignors to Dresser Industries, Inc., Dallas, Tex. No Drawing. Filed Nov. 3, 1967, Ser. No. 680,320 Int. Cl. C04b 35/02, 35/52 U.S. Cl. 106-56 9 Claims ABSTRACT OF THE DISCLOSURE Carbonaceous bonding system for refractories, especially basic refractories, of increased storage life, which system does not normally require heating for use. Said system being mainly comprised of unsaturated fatty acid pitch plus an effective amount of that portion of pitches generally referred to as asphaltenes.

This invention relates to compositions particularly suited for the formation of refractory monoliths. In one aspect, this invention relates to refractory linings of the type found in oxygen converter vessels.

In certain metallurgical processes, such as in the oxygen steelmaking process which has been variously designated as the LD process, oxygen Bessemer process, oxygen converter process or Kaldo process, the basic furnace structure is comprised of a metal skin or shell having a refractory lining interiorly thereof the define the furnace space in which the process is carried out. Generally, the refractory lining of these oxygen steelmaking vessels is comprised of an inner working lining of such as tar bonded, chemically bonded, or burned basic brick, an outer lining adjacent the inner wall of the metal shell usually of a burned magnesite brick, and an intermediate layer.

The intermediate layer is usually monolithic, and is formed by such as ramming of a refractory composition in situ. The intermediate layer can vary in thickness, depending on the vessel being lined and the operating parameters to which the lining is to be subjected. It has been suggested that the composition of the intermediate layer be a tar bonded ramming mix. An example of a prior tar bonded ramming mix, which could be useable to form this intermediate layer, is a dead burned dolomite or magnesite or mixture of dolomite and magnesite with additions of such as creosote, furfuryl, pitch, tar, or the like, as the binder.

When using some types of pitch additions, some difliculty is encountered in the actual installation of the intermediate layer. For example, powdered bond pitch has a melting point in the range 275 to 325 F. In order to obtain the necessary tackiness, plasticity, and workability in such a ramming mix, it is necessary to heat the materials to melt them or to dissolve them in an organic solvent; and this heated mixture is maintained at an elevated temperature prior to and during the actual ramming.

Some mixtures have been suggested which need be heated to only about 100-120 F. to produce a mix which may be worked satisfactorily. However, even this 100 to 120 F. minimum temperature can be difiicult to maintain, particularly during the colder winter months, and requires complicated auxiliary apparatus at an installation site for this purpose.

Even more distressing, however, when using some organic solvents, is that they tend to volatilize excessively when heated, thereby raising the possibility of explosion in a confined working area, as well as the undesirable irritation of the epidermis of the people in the area.

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The invention disclosed in U.S. Pat. 3,256,104 solved the foregoing problems quite satisfactorily. Now, how ever, it has become evident, particularly (1) under certain extreme temperature conditions, (2) when subjected t rough handling, and (3) due to uncontrollable but minor chemical variations in the residual material which the unsaturated pitch is, that the bonding system of the patent will set up" in its shipping container or will lose some of its excellent workability. It is, thus, a primary object of this invention to provide for extending the storage life and workability of unsaturated fatty-acid-pitch-containing carbonaceous bonding systems of the type disclosed and claimed in U.S. Pat. 3,256,104.

Briefly, according to one aspect of this invention, there is provided a basic refractory ramming mix comprised of size-graded, basic refractory aggregate and a nonaqueous, carbonaceous, bonding system. This bonding system is comprised of medium and/ or hard pitch, a selected unsaturated, fluid pitch which is derived from the process of distilling linseed fatty acids and soy fatty acids from linseed oil and soybean oil and an effective amount of asphaltene. Preferably, the total bonding system amounts to between about 3 to 8 parts, by weight, for each parts, by weight, of basic refractory aggregate. The preferred basic refractory aggregate is selected from the group consisting of dead burned dolomite, dead burned magnesite, and sometimes mixtures thereof. In addition, hard burned lime can be used in combination with dead burned dolomite and dead burned magnesite.

In addition to such materials as medium pitch, hard pitch, and creosote, the prior art has taught the use of such carbonaceous materials as bunker C oil, gilsonite, linseed oil, shale tar, asphalt, oil pitches or the type recovered from the distillation and cracking of oils of asphalt, coal, peat, lignite, such materials as heavy water-gas tar, light water-gas tar, oil-gas tar, wood tar, certain types of waxes, and like materials.

This invention further relates to tar bonded or chemically bonded brick of the type useable in the working lining of oxygen steel-making vessels.

An example of a prior tar bonded brick is one of dead burned dolomite or magnesite or mixture of dolomite and magnesite, perhaps also with some hard burned lime, with additions of such as cresosote, furfuryl, pitch, tar, or the like, as the binder.

Briefly, according to this other aspect of this invention, there is provided a basic refractory brick-making mix comprised of size-graded, basic refractory aggregate and a nonaqueous, carbonaceous bonding system. This bonding system is comprised of medium and/or hard pitch, a selected, unsaturated, fluid pitch which is derived from the process of distilling linseed fatty acids and/or soy fatty acids from linseed extracts and soybean extracts and an effective amount of asphaltene. Preferably, the total bonding system amounts to between about 3 to 8 parts, by weight, for each 100 parts, by weight, of basic refractory aggregate. From 2 to 10 parts is satisfactory and up to 12 parts is workable for the brick mix. The preferred basic refractory aggregate is selected from the group consisting of dead burned dolomite (the dead burned dolomite must be stabilized, i.e., combined with dead burning agent, or subjected to a process to obtain an equivalent stabilized product), dead burned magnesite, and sometimes mixtures thereof. In addition, hard burned lime is sometimes used in combination with dead burned dolomite and dead burned magnesite.

In addition to hard pitch, medium pitch and creosote, the prior art has taught that the various other carbonaceous materials mentioned above can be used in brick mixes.

Some prior workers, in selecting various materials of 3 the carbonaceous bonding constituents noted above, for both monolith forming mixes and brick mixes, have further suggested the inclusion of lubricating additives, such as petroleum jelly, kerosene, gasoline, benzene, and like petroleum derivatives in order to obtain the desired workability, plasticity, and/or tackiness. Of course, these latter petroleum derivatives considerably increase the danger of explosion and fire. Still other Workers have suggested various wetting and dispersing agents which would facilitate formation of aqueous colloidal suspensions or emulsions. It is well known to those skilled in the art that water is an undesirable constituent with mixtures of basic refractory materials, because of hydration and subsequent danger of cracking.

The unsaturated fatty acid pitches of this invention are within the group sometimes referred to in the art as fatty acid pitches, which group designation is generally used to described residual material obtained in fractional di tillation of animal and vegetable materials such as lard, tallow, palm oil, and other vegetable materials, bone fat, garbage and sewage, wool grease, and packing house waste. The residual material, which is termed fatty acid pitch, is usually a dark brown to black, uniform to lumpy, gritty and thick material substantially free of saturated fatty acids.

The fatty acid pitches, which are used in this invention, according to a preferred embodiment, are those obtained from the distillation of linseed extracts and soybean extracts to recover linseed fatty acids and soybean fatty acids. These materials are fluid, as distinguished from waxy or soapy, at room temperatures of about 70 F. The linseed pitch has an acid number in the range 30 to 60, a viscosity (Stormer viscosity, seconds at 25 F.) of 150 to 350, and an iodine value of 110 to 125. The soybean pitch has an acid number in the range 30 to 60, a viscosity in the range 50 to 200 (Stormer viscosity, seconds at 20 C.), and an iodine value of approximately 100 to 110. As indicated by the acid number value, there is considerable free fatty acid in both pitches. The e pitches, again in view of their iodine value, are sometimes called unsaturated fatty acid pitches. As would be expected, the pitches consist essentially of carbon, hydrogen, oxygen, and nitrogen atoms.

According to preferred practices, a brick mix or monolith is bonded with the following carbonaceous sy tem:

( 1) 1 to 2 parts, per 100 parts, by weight, of refractory of unsaturated soybean pitch,

(2) 1 to 2 parts, per 100 parts, by weight, of refractory of asphaltene-containin g material sold by The American Oil Company under the designation Petroleum Compound #9.

According to the best mode now known, we use 1.5 parts of each of the soybean pitch and asphaltene per 100 parts, by weight, of basic refractory.

The foregoing bonding system can further be mixed with most any of the many other pitches and organic materials listed above as known to the art for inclusion in refractory mixes.

As is understood by those in the art, hand pitch is added to the mix to obtain as much fixed carbon as is commercially feasible. Since my unsaturated fatty acid pitches do not require solution of the hard pitch for tackiness, one can also use such as graphite or lamp black as the source of the carbon. Gilsonite could also be used. The total quantity of bonds, however, will contain at least about 2 parts, by weight, of our selected unsaturated fatty acid pitch and asphaltene whether hard pitch, medium pitch, graphite, lamp black, or the like constitutes the remainder of the bonds. The foregoing is true in both monolith and brick mixes according to the invention.

Also, where little or no fixed carbon is neces ary, it is possible to use our unsaturated fatty acid pitches and asphaltene alone. Further, where little fixed carbon is 4 required, the fatty acid pitches can be used in combination with various polymers, such as acrylics, polyamides, polyesters, epoxies, and the like to obtain a thermo-setting bond.

Typical and preferred sizing for refractories according to the invention is as follows:

Screen Analysis (Tyler Series) Percent, about /2" to particles held on a 6 mesh screen 20 Passing the 6 mesh screen and resting on a 28 mesh screen 35 Passing a 28 mesh screen 45 28 mesh material held on a 325 mesh screen 40-60 Magnesite, Dolomite,

percent percent Silica ($102) ea. 0. 7 ca. 1. 2 Alumina (A ca. 0. 3 ea. 0. 8 Iron oxide (Fez 3).. ca. 0.3 ca. 5.0 Lime (CaO) ca. 2. 3 ca. 53. 0 Boron (B2Oa) 0. ()3 0.03 Magnesia (MgO ca. 38. 9

l Remainder, by difierence.

In a broader aspect of the invention, the refractory aggregate used for making our monolith forming mixes and in the brick mixes need not be basic refractory. Further, in less critical areas of the oxygen converter vessel, such as the intermediate and vessel backup portions of the lining, it is possible to use basic refractory materials other than dead burned magnesia, dead burned dolomite, and lime (calcia); for example, forsterite, olivine, chrome ore, and the like. The unique properties of our bonding material also makes them desirable for use with refractory aggregates such as calcined fire clays, ganisters, high alumina materials such as diaspore, Alabama and South American bauxite, kyanite, alumina, and mullite. It can be used with mixtures which include silicon carbide and the like if one so desires, further including zircon, zirconia, and other well known refractory materials used for the manufacture of monolith forming mixes such as ramming mixes and brick mixes.

In the foregoing discussion, we specifically mentioned the unsaturated fluid pitches recovered from the distillation of fatty acids from linseed oil or soybean oil. It is, of course, understood that the unsaturated pitch residue of the distillation of fatty acids from other vegetable oils are satisfactory for the practice of this invention. However, the selected fluid pitch should be characterized by physical properties similar to those set forth above, i.e., liquid or fluid at room temperature, characterized by extensive unsaturation (as measured by iodine number) and capable of imparting the necessary tackiness, workability, and plasticity to the ramming mix in which they are included.

The following tables are indicative of comparative laboratory testing according to the invention. Part I deals with formed shapes, and Part II deals with loose material of the type one uses for forming a monolith. Soybean pitch I is a superior pitch as compared to soybean pitch II. These pitches came from two dilferent lots of commercially purchased material and indicate that some variation can be expected even though, according to the present invention, both pitches work.

PART I.(FORMED SHAPES) A B C D E F (Control) (Preferred) (Control) (Preferred) Base mix: Magneslte of analysis given above:

-4 mesh --..36% l0+28 mesh BMF (55 Additions (parts Soybean pitch I: Soybean pitch II: 3 2 1. 5 Petroleum compound No. 9:- 1 1 l. 5 Forming pressure: 3, 000 p 1 Bulk density, dry, p.c.f. (average 5) 176 176 ND 1 177 176 Load to crush, after drying 250 F. (average 3) p.s.i: 460 120 180 ND 1 230 140 1 Not determined.

PART II.(LOOSE MATERIAL) A B C D E F (Control (Preferred) (Control) (Preferred) Storage tests-room temperature:

After 2weeks Damp. Loose. Good Same as A Same as A Dry. Loose. Poor Damp. Soft com- Same as E.

hall in hand. ball hand. pacted. Fair to poor hall in hand. After 3 weeks Damp. Loose. Fair No change No change-. No change Slight damp. Soft comball in hand. pacted.Fair ball inhand. After 4 weeks Slight damp. Damp. Soft com- No change.

koiilse. Slight pacted. Good ball.

a After 5 weeks No change No change Storage testsat 140 F After 2 days Slight damp. Damp. Loose. Same as B Inferior to A Same as A Same as A.

Slight com- Good ball pacted. Fair in hand. ball in hand. After 7 days Dry. compacted. Damp. Slight No ball in compacted. hand. Good ball in hand.

1 Loaded with 100 lbs. weight.

The results of the storage tests are obviously subjective, in that ones sense of feel is involved, i.e., it is preferred that the material be damp, loose, i.e., not compacted, and that one be able to grab a handful of the material and easily form a good, firm ball of material in ones hand. With this explanation in mind, a comparison is suggested between Mixes A and B on the one hand, and D and F on the other. A and D are control mixes; B and F are according to the invention. Note that after 7 days Mix B, including the asphaltene, was still damp, relatively loose, even though slight compaction had occurred, and a good ball was still easily made in the hand. A comparison of Mixes D and F, made of the less desirable soybean pitch, F including the asphaltene, produced a similar result.

The useful range of asphaltene is that which is effective in improving the storage life of the soybean pitch bonding systems. Earlier in this specification we mentioned preferred and optimum proportions for the asphaltene and soybean pitch. We also mention that the total quantity of organic bonding material can be between 2 and 12 parts, by weight, based on the total weight of refractory. Based on present experience, the lowest limit for the asphaltene in such a system is about 0.5 part, by weight, and an upper limit is about 6 parts, by weight, per 100 parts, by weight, of refractory. In these carbonaceous systems, the soybean pitch can range from 0.5 to 11.5 parts, by weight, per 100 parts, by weight, of refractory.

It is thought a brief discussion of asphaltenes would be useful for a more complete understanding of the invention. Asphaltenes are a characteristic constituent of asphalt which serve to distinguish it from all other petroleum products. The asphaltenes are defined as the nonmineral constituents of asphalt which are insoluble in naphtha. The naphtha for this purpose must be petroleum derived and composed entirely of open ended hydrocarbons, and test exactly 88 Baum, equivalent to a specific gravity of 0.638, at 60 F. At least 85% by volume of naphtha should distill between 95 and 150 F.

All asphalts do not include the same percentage of asphaltenes. For example, Trinidad asphalt contains 37%,

Mexican residual asphalt 20%, and Texas residual asphalt 9 to 17%.

Also, when we use the word or terminology asphaltene herein, we are describing a material predominantly characterized as asphaltene which will have the storage life-extending properties in refractory bonding systems of the type disclosed and claimed herein. Thus, it is not essential that the asphaltene material be substantially pure, and it may include appreciable quantities of other organic constituents; but the material must be liquid at temperatures of use and preferably liquid at 70 F. For example, 50% by volume of nonasphaltene organic constituents chemically compatible with the refractory and unsaturated fatty acid pitch could be used. The important thing, is that sufiicient asphaltcne be present to provide the effect demonstrated by the data above.

In the foregoing discussion, all parts and percentages are by weight, all refractory chemical analyses should be considered but typical and are on an oxide basis, in conformity with the normal practices of reporting the chemical constituents of refractory materials. All sizing is according to the standard Tyler series of screens or sieves, unless specifically noted to the contrary.

Having thus described the invention in detail and with sufficient particularity to enable those skilled in the art to practice it, what is desired to have protected by Letters Patent is set forth in the following claims:

We claim:

1. In refractory batches bonded with selected nonaqueous, carbonaceous bond materials which batches consist essentially of about parts, by weight, of refractory and on the order of 2 to 12 parts, by weight, of the bond material, said bond material including an unsaturated fluid pitch which is the residue recovered from the distillation of vegetable oils to remove fatty acids therefrom and in a quantity sufficient to obtain workability, plasticity, and tackiness in the batch when installed in the situs of use, the improvement consisting essentially of said bond material including asphaltene material in a quantity sufficient to extend the storage life and workability of the batches.

2. The batches of claim 1 in which the fluid pitch is selected from the group consisting essentially of linseed pitch and soybean pitch.

3. The batches of claim 1 in which the bond material includes a nonaqueous, carbonaceous material, solid at room temperature, which provides a coke residue at elevated temperatures and selected from the group consisting of medium pitch and powdered hard pitch.

4. The batches of claim 1 in which the bond material further includes materials selected from the group consisting of graphite, lamp black, and mixtures thereof.

5. The batches of claim 1 in which the carbonaceous bond includes the fluid pitch and material selected from the group consisting of graphite and lamp black.

6. The batches of claim 1 in which the bond material consists of 1.5 parts, by weight, each of the unsaturated pitch and the asphaltene, per 100 parts, by Weight of refractory.

8. The batches of claim 1 in which the refractory is basic refractory.

9. A formed refractory made of a batch according to claim 1.

References Cited UNITED STATES PATENTS 3,222,196 12/1965 Davies et al. 106-58 3,256,104 6/1966 Weaver l0656 3,340,075 9/1967 Stoddard et al l0656 JAMES E. POER, Primary Examiner U.S. Cl. X.R. 

